The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the inventors hereof, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly not impliedly admitted as prior art against the present disclosure.
The present disclosure relates generally to memory systems and methods, and in particular to systems and methods for error recovery in memory systems that use iterative codes.
In the last several years, the hard drive (HDD) industry has started transitioning from memory system architectures using Reed Solomon (RS) Error Correction Codes (ECC) to memory system architectures using iterative (ITR) codes. The first generation of iterative architectures featured a concatenation of inner iterative code with outer RS ECC. The second generation iterative architectures have completely removed the RS ECC. Such second generation architectures referred to as RS-less ECC architectures.
Iterative codes have a distinct advantage over RS codes with regard to error correction of random-noise type of errors. For example, since most errors that are due to random noise have low reliability, the usage of soft decisions by an RS-less decoder can result in significant storage capacity gains (or, equivalently, in lower signal-to-noise ratio (SNR) operating points) when compared RS ECC decoders, which operate using hard decisions.
However, iterative codes are particularly vulnerable against certain types of “exception errors”. A large number of consecutive errors within received data (due to, e.g., media defects or thermal asperities) may be easier to correct via an RS code then via an iterative code. This is especially the case when the soft information provided to the iterative decoder is in error and strongly points in the wrong direction.
Since a significant portion of hard failures in HDD memory systems are driven by exceptions, systems and methods are needed that can sustain stringent data reliability standards while allowing HDD industry to reach new capacity milestones.